Workholder for a lapping machine



Feb. 14, 1961 A. N. GARTHWAlTE ETAL 2,971,298

WORKHOLDER FOR A LAPPING MACHINE Filed 001;. 5, 1958 4 Sheets-Sheet 1 INVENTORS Feb. 14, 1961 A. N. GARTHWAITE EIAL 2,971,298

WORKHOLDER FOR A LAPPING MACHINE Filed 001;. 3, 1958 4 Sheets-Sheet 5 ,MberZ /V. Haiku/@556 ATTORNEYS Feb. 14, 1961 A. N. GARTHWAlTE ETAL 2,971,298

WORKHOLDER FOR A LAPPING MACHINE Filed 001:. 3, 1958 4 Sheets-Sheet 4 r I l .allel surfaces of a workpiece. principal object of this invention to provide a workholder =for,a lapping machine of the class described above Wherein the workpiece is rigidly held with a surface thereof referenced to the conditioning ring, therefore the lapping .plate will abrade the workpiece such that a surface WORKHOLDER FOR A LAPPING MACHINE FiledOct. s, 1958, set. No.'765,1 55 8 Claims. (01. 51-131 This invention relates to workholding devices and more particularly to a workholding device adapted to be sefcured to a wear ring of a lapping machine for holding a workpiece to be lapped or ground thereby.

1 One type of lapping machine in widespread use has a large annular rotatable lapping plate, with one radial face which is utilized for lapping articles. A plurality of conditioning rings or wear rings are associated with the lapping plate, and these wear rings bear against the surface of the lap and help maintainthe lap surface in substantially fiat condition. The workpieces to be lapped may be placed loosely within the wear rings, or they 'may be attached to a workholder which is associated with the wear rings. Hence, the wear rings may also contain the workholder as well as constantly condition 'thesurface of the lap. To prevent the articles from constantly contacting the same portion of the surface of the United States Patent a lap and tracking thereon, the wear rings are rotated about "their own axis by various means.

There are numerous types of workholding devices which are'used with the classof lapping machines out lined above. However, in all the known types of workh'olding devices for this class of lapping machine the s irface of the work is allowed to assume an angular position with respect to the plane of the lapping surface.

Thus, if one surface of the workpiece is at an angle with respect to an opposite surface or other reference surface whenlapping is begun the lapping will not cure this unevenness but will merely remove the material and leave the lapped surface at the same angle with respect to the opposite surface or reference surface. An-

. other deficiency of the known type workholders is the possibility of producing a rounded surface of the work- 'piece to be ground occasioned by the fact that the workpiece may be slightly tilted if it is not rigidly held par- --allel with that portion of surface of the lap acting upon the workpiece. The large annular lapping surface has "a tendency to wobble upon rotation, hence not all portions of the lapping surface will be parallel at all times face may be used as the reference plane for lapping par- Accordingly, it is the thereof is lapped with reference to a predetermined surface thereon and there will be no rounding of the lapped surface ofthe workpiece held bythe workholder Although it is known to provide a workholding device or a lapping machine with a stop to limit the depth of invention to provide a workholder for a lapping machine 2,971,298 Patented Feb. 14, 1961 ICC having an easily visible and simple adjustable stop device be in the nature of a micrometer.

In the known workholders for lapping machines the weight or force applied to the article to be lapped is supplied by the weight of the article itself or the weight of the article plus the weight of a portion of the workholder and the force applied to the article is not adjustable. It is sometimes desirable to apply an adjustable or variable downwardly acting force to the article to be lapped in order to determine the speed and degree of fineness of the lapping. It is therefore a further object of this invention to provide an adjustable biasing means in combination with a workholding device to adjustably control the downward force applied to an article to be lapped and thereby control the speed and results of the lapping operation.

An additional object of this invention is to provide a workholder which is quickly and easily removable to allow an inspection or unloading and loading of the work plurality of wear rings associated therewith for continuouslyconditioning the lapping surface, the wear rings being rotatable about their ownaxis and not travelling with the rotatable lapping plate. 'The workholder of this invention is rigidly attached to the wear rings and the work is rigidly attached to the workholder suchfthat the surface of the work to be lapped will always be fixedly referenced with respect to another surface of the workpiece. The workholder and the work held rigidly thereon are movable only in adirection perpendicular to the plane containing the surface of the lap beneath the wear ring and are not rotatable with respect to the wear ring. Hence the surface lapped is not angularly tiltable with respect to the plane of the lap and the top and bottom surfaces of the wear ring. A micrometer stop means is piece against the surface of the lap. In the other modification the workholder is adapted to lap asurface of a workpiece inclined at an adjustable predetermined angle to another surface of the workpiece. In this. modification the lower end of the workholder to which the work is secured is adjustable with regard to the vertically movable portion of the workholder, thus providing an angle "which may be accurately adjusted for lapping various angularsurfaces on workpieces. Again, the workholder is movable only in a direction perpendicular to the plane of the lapping surface. A split bushing may be provided for quickly and easily removing the portion of the workholder containing the workpiece from the fixture for workpieceloading and unloading and/or workpiece inspection.

Other objects of the invention will be pointed omit:

the following description and claimsand illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and. the best mode which has been contemplatedgof applying that: principle.

In.the.drawings:; s: a I1 r Fig. 1 is a top plan view of a lapping machine showing the workholder of this invention associated therewith;

Fig. 2 is a side elevation'v iew, partially insection; showing a workholderof this invention attached to a wear ring associated with the lapping machine;

Fig; 3, is a sectional view taken along line 3 3 of Fig. 2; i

Fig. 4 is a side elevation view showing a modification of a workholder utilizing the principles'of this inventon;

Fig. 5 is a sectional view taken along line 55 of Fig.4;

Fig. 6is a sectional view taken. along line 6-6 of Fig. 4;

Fig. 7 is a sectional view taken along line 7-7 of Fig. 6;

Fig. 8 is a sectional view taken along line 88 of Fig. 4.

Referring to the drawings, Fig. l's-hows a lapping machine 10 which has a large annular rotatable lapping plate 12. A pluralityof wear rings 14 are associated with the lapping surface 12 for continuously conditioning the lapping surface and maintaining this surface relatively Hat and smooth. The wear rings are rotatable about their .own axis in a direction as shown by the arrows in Fig. 1

and this rotation is, in the illustrated embodiment, induced by the rotation of the lapping plate 12. A yoke 16 may be adjustably mounted by a slot and nut arrangement 17 to position rollers 18 to bear against the edges of the wear ring 14. The location of the yoke relative to the lapping plate is adjusted so that the conditioning rings 14 cause even wear on lapping plate 12 and therefore maintains a flat lapping surface on the lapping plate. Adjustment of the conditioning rings can be controlled to provide more rapid wear on either the inner or outer edge of the lapping plate thus maintaining flatness of the lapping plate while work is being done. This general arrangement is described in detail in the patent to 'Roshong--2,627,144, granted February 3, 1953.

The workholder 20 of this invention is shown in detail in Fig. 2. The workholder of this embodiment is for lapping flat articles such that the surface to be lapped will be parallel with the opposite, surface of the article. The wear ring 14 has opposite parallel surfaces 22 and 24, thus if surface 22 is bearing against, lapping plate 12 then surface 24 will be parallel to lapping plate 12. The workholder includes a supporting structure 26 having a flat lower surface 28. This support 26 is rigidly attached to the wear ring 14 by suitable screws 30. Supporting structure 26 includes an upright portion 32 to which is secured an overhanging top portion 34.

The top portion 34 and the supporting structure 26 have apair of bosses 36 thereon forasupporting ball bushings 38 therein. A vertically movable workholder 40 includes a work-attaching plate 42. The work-attaching plate may have a plurality of holes 43 therein for attaching the workpiece thereto by screw means or the workpiece mayibe attached thereto by special adhesive tape as is well known in the grinding and lapping art. The bottom surface 44 of workpiece holder 42 is, by the above-described arrangement of parts, always parallel to the top surface 24 of the wear ring 14. Thus, anyworkpiece attached to the surface 44 of workholder 42 will be lapped such that its opposite face is parallel to the face attached to surface 44. i

In order to prevent the workholder 40 from rotating, a groove 46 is provided therein and this groove cooperates with a key 48. Key 48 is held in key support 50 which in turn is secured to the top support portion 34 by suitable screws 52.

Means are provided to adjust the amount of lapping to be accomplished. This means includes a micrometer to vertically moving workholder 40 by a suitable clamp 59. Thus the anvil 57 of micrometer 54 can be set to stop the downward movement of workholder 40 at any predetermined position thereby determining the amount of material to be removed by the lapping operation.

Means are also provided-foradjusting the downward force appliedtothe workpiece and thereby adjusting the speed and fineness of the lapping operation. This means includes a coil spring 60having one end abutting the lower ball bushing 38 and the other end abutting an: adjustable nut 61 on the movable rod 40. Nut 61 is threaded on screw threads 62 of workholder 40 for adjustment purposes. Spring 60 thus biases, workholder 40 upwardly. An oppositely acting spring 63*is provided and this spring abuts upper ball slide bearing 38 and nut 64. Nut 64 is similarly adjustable on threads 62 of rod 40. By adjusting nuts 61 and 64 the bias that springs 60 and 63 supply to workholder 40 may be adjusted and therebythe force applied downwardly to the workpiece causing the workpiece to contact the lapping surfacefwith more or less effective Weight may be adjusted. A weight '65 may be appliedto supporting structure 26 to balance the weight, applied to the opposite sides of the wear ring 14.

The embodiment rhown in Figs. 1 through 3, is espe-' cially adapted to accurately lap one surface of a flat workpiece parallel with the opposite surface thereof and adjust the amount and degree of lapping. If it were desired to lap a surface of a part on an angle with reference to another surface thereof and to quickly and. easily remove the part lapped for inspection or to remove the workpiece from the workholder, the workholding device shown in Figs. 4 through 8, which is a modification of the device shown in Figs. 1 through 3, could be used. In the workholder shown in Figs. 4 through 8 the same principles are involved, i.e., the work is rigidly held by a workholder, the workholder is allowed to move only perpendicular to the'plane of the wear ring surface, and the supporting structure is rigidly secured to the wear ring. Referring now to Fig. 4, a supporting structure 66 having a fiat lower surface 67 is rigidly secured by screw means 68. to the upper surface 24 of the wear ring 14. The supporting structure 66 extends upwardly from opposite sides of the wear ring and is provided with a top crossing member 70 secured thereto by screws 71. Top crossing member 70 includes a boss 72 for a split ball bushing 74. This split ball bushing 74, as shown in Fig. 8, is split across one side and this split side is accurately aligned with an opening 76,.on]

. same width as slot 76 and bears against the edges thereof 54 which is rigidly held ,by a clamp 56 integral with the t top support portion 34. The anvil 57 of. the micrometer 54 is adapted toabut against 9. lug 58. .which is secured to thus effectively guide'the rod '76 in vertical movement while preventing any rotation about the axis thereof. The lower portion of rod 78 includes a reduced diameter section 85 having a diameter less than the width of slot 76. Thus, when it is desired'to remove the rod' 78 and the workpiece secured thereto, it is only necessary to move the rod 78 upwardly until the reduced diameter portion 85 is within the split bearing 74, then the rod 78 may be moved forwardly such that the reduced di- 1 ameter portion 85 clears the slot '76, i.e., therod 78 may be moved to the position shown in phantom lines in Fig. 8,'thus easily and'quickly removing the workpiece.

In a manner similar to the embodiment'of Figs. 1-3,

stop means may be provided for adjustably the adapted to bear upon the top surface of cross member 70. 2 The micrometer is held by the clamp member 88 and this clamp member isin turn clamped to rod 78 by a clamp means 90.

The work to be lapped may be heldin a workholding member 91 attached to the lower end of movable rod 73. As shown in detail in Figs. 6 and 7, workholding member 91 is generally U shaped and includes a central member 92 attached to rod 78 and side members 93 attached to member 92 by suitable screws 94. A work supporting plate 95 is angularly movable about the axis of a bolt 96 such that any workpiece held thereon may be IIIOVed in a similar manner. The workpiece may be secured to the plate 95 by suitable screw means threaded in holes 96' or by adhesive tape means as well known in the art. An angle indicating pin 97 is secured to plate 95 by a screw 98. This pin extends to the outside of side plate 93 through a slot 99 and provides an indication of the angle that plate 95 is inclined. This indication is defined by means of a fiducial mark 100 inscribed on the outer face of pin 97 which cooperates with a scale 102 on a scale plate 104secured to the outer surface of side plate 93 by screws 105. A holding plate 106 which has'actuating screws108 secured thereto is provided to rigidly hold the workpiece after the angular inclination thereofhas been set. By actuating screws 108 plate 106 may be forced against the side of the workpiece opposite plate 95 to rigidly hold the workpiece during the lapping operation;

The device functions in operation as follows: A workpiece is secured either to workpiece supporting plate 42 or to workpiece supporting plate 95 and the workholder assembly is secured, to the wear ring 14. The lapping plate 12 is rotated thereby inducing a rotation of the wear ring and suitable lapping compound may be applied to the surface of the lapping plate as is well known in lapping operations. During rotation of the lapping plate 12 it will inherently tend to wobble slightly; however, the surface of wear ring 14 will follow the surface of lapping plate 12 thereunder. Since the surface to be lapped is dire tly referenced to the supporting structure and the supporting structure cannot be angularly tiltable with respect to the plane of the lap, no rounding of the surface of the workpiece will occur. Furthermore, in the Figs. 1-3 modification the surface of the workpiece lapped will always be parallel with the opposite surface of the workpiece. In the Figs. 4 through 8 modification the surface of the workpiece lapped will always be 'at any desired adjusted angle. This is radically different from the known workholders wherein the workpiece is allowed to loosely follow the lapping surface such that the surface lapped on the workpiece would always be parallel to the original surface before the lapping conmenced.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to the preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation ma y be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. An apparatus for holding a workpiece upon which a true flat surface is desired to be formed, said apparatus adapted to be used with a lapping machine having a rotatable lap with a lapping surface capable of producing by abrasion the desired true surface on the workpiece, said apparatus comprising; a rotatable annular wear ring having parallel end faces and an internal di- :nneter substantially larger than the workpiece surface to be lapped, the lower end face of the wear ring adapted to frictionally bear upon the lapping surface, a supporting structure rigidly secured' to the annular wear ring, a rigid upwardly extending portion of the supporting structure, a slide bearing contained within the up wardly extending portion of said supporting structure, a vertically movable workholder adapted to rigid hold a workpiece having a surface thereon desired'to be lapped, a journal portion of the workholder cooperating with the slide bearing for slideably mounting the workholder for vertical movement only, means cooperating between the upwardly extending portion of the supporting structure and the workholder to prevent rota- ;tional movement of the workholder about an axis in the direction of vertical movement of the workholder, whereby a surface of a workpiece desired to be lapped and rigidly attached to the workholder may move only perpendicular to the plane of the lap and will always be parallel to the plane defined by the lower end of the wear ring.

2. An apparatus as defined in claim 1 further comprising, spring means cooperating between said slidably mounted workholder and said supporting structure for ,adjustably biasing said workholder away from the lapping surface to thereby adjustably control the force applied to the workpiece-by the workholder as lessened by the adjustable bias of said spring means.

3. An apparatus as defined in claim 1 and further comprising an adjustable stop including a micrometer co- :opcrating' between the upwardly extending portion of thesupporting'structure and the vertically movable workholder to limit the amount of movement of the workholder and thereby control the amount of material re- .moved from the work by the lapping surface.

4. An apparatus as defined in claim 3 further comprising an adjustable nut threaded on said workholder below the journal portion thereof, a spring surrounding the workholder having opposite ends thereof abutting against said adjustable nut and said supporting structure so that a biasing force of said spring opposes the weight of said workholder whereby adjustment of said nut will vary the biasing force of said spring to control the'force applied to the workpiece against the lapping surface.

5. In combination with a lapping machine of the type having a rotatable lap with a lapping surface, an improved apparatus for holding the work to be lapped, the apparatus comprising; an annular wear ring having parallel upper and lower end faces, the lower end face of the wear ring adapted to frictionally bear against and move upon the rotatable lapping surface, the wear ring serving to maintain the lapping surface in condition, a supporting structure secured to the upper end face of the wear ring, an upright portion of the supporting structure extending vertically upwardly from the wear ring, an overhanging top support secured to the upright portion and extending across the wear ring, a workholder structure adapted to rigidly carry work to be lapped, a slide bearing contained within the overhanging top support, a journal portion of the workholder adapted to cooperate with the slide bearing contained within the supporting structure for mounting the workholderfor vertical movement only, and guide means on the overhanging top support and workholder cooperating to prevent rotational movement of the workholder about an axis in the direction of vertical movement, so that work rigidly secured to the workholder can move only perpendicular to the lapping surface under the wear ring and the surface to be lapped will always be maintained parallel to the parallel end faces of the rotatable wear ring.

6. An apparatus for forming a true surface of predetermined contour upon an article, said apparatus comprising; a rotatable lap capable of producing by abrasion the desired true surface, a wear ring rotatably mounted with respect to and frictionally bearing upon the lapping surface, said wear ring serving to maintain the surface in condition to produce the desired true surface on the article, said rotation of the lap inducing a rotationinlthe wear ring, workholding means for hold ing the article on the surface of the lap, 'structural supporting means fixed to said wear ring to support the workholding means for vertical movement only and to prevent relative angular movement between the workholding means and the wear ring hence allowing'the sur face of the article on the lap to move only perpendicular to the surface of the lap, and an angularly adjustable attachment for the workholding means for holding a surface of the work to be lapped at an angle with respect to a reference surfaceon the work, and a scale for indicating the angle of the surface lapped.

7. An apparatus for forming a true surface of predetermined contour upon an article, said apparatus comprising; a rotatable lapcapable of producing by abrasion the desired true surface, a wear ring rotatably mounted with respect to and frictionally bearing upon the lapping surface, said wear ring serving to maintain the surface in condition to produce the desired true surface of the article, said rotation of the lap inducing rotation in the wear ring, workholding means for holding the article on the surface of the lap, structural supporting means fixed to the wear ring and cooperating with the workholding means to prevent relative angular movement between the workholding means and the wear ring and to allow the surface of the article on the lap to 5 'of producing by abrasion the desired true surface and at leastone wear ring rotatably mounted with respect to' said lapping surface and frictional'ly bearing thereon to continuously condition the abrasive lappingsurface; said workholding apparatus comprising; a workholder l0 rigidly, holding a workpiece upon which the surface is desired to be generated with another surface of the workpiece referenced against the workholder, asupportling structure for supporting the workholderfor movement perpendicular to the plane of the lapping surface 15 while preventing relative angular movement of the work- .holder to the plane of the lapping surface and to the surface of the wear ring, means of securing the supporting structure to the wear ring, an adjustable-split bushi ing at the supporting connection between the workholder 9 and the supporting structure whereby the workholder may be moved perpendicular to the plane of the lap a predetermined amount and then may be removed through the split bushing to allow visual inspection and loading or unloading of the workpiece carried by the work 25 holder, and an attachment for the end of the. workholderadjacent the lapping surface, said attachment hav ing an. angularly adjustable member carrying the work whereby the work may be angularly adjustable with remove only perpendicular to the surface of the lap, and a 30 Spec to h Surface of the split bushing on said supporting means allowing said workho'lding means to be moved perpendicularly up wardly and removed from the structural supporting means for workpiece loading and unloading.

References Cited in the file of this patent UNITED STATES PATENTS 2,634,558 Wolfskill Apr." 14,1953 

